Confectionery magnate Petro Poroshenko claimed Ukraine's presidency on Sunday after exit polls gave him a clear absolute majority of first-round votes and he pledged to steer the ex-Soviet state into the European mainstream.

"All the polls show that the election has been completed in one round and the country has a new president," said the burly 48-year-old billionaire who has long experience in government.

At his campaign headquarters, he told supporters the majority of Ukrainians had given him a mandate to continue a course of integration with the rest of Europe but said his first priority was to travel to the east of the country to end "war and chaos" caused by pro-Russian separatist rebels.